Marshall power amp voltages

[mike3124]

Hi Folks;
Does anyone know what voltage the secondary windings on the T4145 mains transformer used in the 100 watt Marshall power amps are?

I have googled the world but this seems to be the BEST kept secret in the world.

This seems daft as I'm hardly going to wind the transformer myself and will end up buying one but I would like to know . I'm guessing the HT is about 470 volts.

The heater winding is 6.3 v (no secret there) I believe the winding with the white output lead is 100 volts (and I'm guessing that's supplying grid bias to the four EL84 power tubes.

power handling for the mains transformer should be 200 Watts.

Any helpful soul out there who can confirm?

Thanks

Mike

[Enzo]

Be fair to Marshall. They don;t bother to publish voltage and current specs because they already told you the proper transformer is the T4145.

But if you want to find one on your own, consider that it is a 100 watt amp with four common power tubes. There is nothing to make it any different from ANY 100 watt four power tube amp. They all run in the 475-500v range, they all need the same current for the 100 watts, and they all need about the same current for the preamp. They may or may not have a bias winding or tap, but if they do, it will be about the same for all - maybe 50v.

But all that aside, if you want 470VDC, and you are not using a rectifier tube, then you are going to need about 335VAC, or 770VAC-CT. That depends upon your rectifier choice.

[mike3124]

What you say is true, Marshall do provide the part number but I wanted to understand what and why.

You have helped with that and I appreciate it.

Thanks

Mike

[Enzo]

And welcome to the forum.